Treatment of oil producing sands



alented Feb. 2, i945 TREATMENT OF OIL PRODUCM G SS Philip H. Jones, lRedondo Beach, and Marcellus T. Flaxman, Inglewood, Calif., asslgnors to Union Oil Company of California, Los Angeles, Calil., a corporation of California No Drawing. Original application April 25, 1939, Serial No. 269,910, now Patent No. 2,342,106, dated February 22, 1944. Divided and this application April 13, 1943, Serial No. 482,940

2 Claims.

This invention relates to the production of oil from oil-producing formations and particularly to a method of increasing the efiective permeability of oil-containing formations immediately surrounding a well bore hole and is a division of our co-pending application Serial No. 269,910.

filed April 25, 1939,now Patent No. 2,342,106,

granted Feb. 22, 1944.

In the drilling of oil and gas wells, particularly by rotary tool methods. it is conventional to employ a drilling fluid to aid the drilling operations. The drilling fluid, generally an aqueous suspension of solid matter, such as clay, bentonite or other similar material or even plain water, is circulated down through the drill stem around the tool or drill bit employed for the drilling operation and rises between the drill stem and from blowing in prematurely. The prevention v of the blowing in or the entrance into the bore hole of the high pressure fluids contained in the penetrated formations requires that the drilling fluid be at a relatively higher pressure than that contained in the pentrated formations. In order to insure that the pressure of the drilling fluid shall be sufliciently great, it is conventional to add to the drilling fluid such weighting materials as barytes, hematite or finely divided iron when the clay content of the said fluid is not in itself sufficient. The producingformation being pervious and the drilling fluid thus being under a relatively high pressure head at the level in the bore hole adjacent the producing formation. a

" for removing water from producing formations tension than oil for the surface of the. sand parsand grains and capillaries. In any event, whatever is the actual physical state of the water in the producing formation, its presence in the producing formation actually greatly reduces the effective porosity and permeability of such formations immediately surrounding the bore hole with the result that the rate at which oil or gas or mixtures thereof can subsequently pass through such formation in flowing to the well is greatly reduced.

Therefore, it is apparent that if the water in the oil or gas-producing formations could be removed from these structures in the immediate vicinity of the well bore hole, the effective permeability of the formation and the production rates from such a well could be appreciably increased.

It is accordingly an object of this invention to provide a treatment for removing water from the oil or gas-producing formations immediately surrounding the well bore hole and thus to increase the effective permeability of such formations and the productivity of the well.

It has been discovered that the removal of water from the producing sands can be effectively accomplished by subjecting them to the washing action of so-called soluble oils which are capable of lowering the surface tension forces holding the water in the sands and of dissolving or emulsifying the water.

The wash oils which have been found suitable are in general the so cailed soluble oils having the ability to disperse spontaneously in'water and under some conditions the property of apparently dissolving both the oil without visual occurrence of two phases. It is probable that such oils form emulsions with the water which in some cases where the refractive indlces of the oil and water phases are substantially equal which cannot be distinguished from a homogeneous solution by ordinary visual inspection. However, when an excess of water is taken up with the soluble oil, it finally assumes the appearance of an emulsion but the dispersed particles are found to' be exceedingly small and readily able to pass through the small capillaries, such as occur in permeable oil-producing formations.

Soluble oils which have been found to be suitable are in general the 'sulfonated mineral and vegetable oils and the water-soluble salts thereof. For example, sulfonated castor oil and'sulfonated olive oil have been efiective. A sul fonated mineral oil, such as that produced as a by-product by the heavy acid treatment of a petroleum fraction to give what is known as awhite oil, and the sodium or'potasslum salts of such sulionated oil has been found to be efiectlve. 1

A compounded soluble oil containing the before mentioned sulfonated mineral oil which has been found to be particularly suitable for treating wells to increase the eflective permeability of the surrounding oil-producing formation comprises a mixture of the following materials:

Per cent by weight A sulfonated petroleum fraction, such as PB emulsifier manufactured by Sonne-' born and Sons (sodium and/or potassium Other soluble oils made with other emulsifierswhich are useful as wash oils are as follows:

Per cent Potassium naphthenate 15.0

A high naphthenic lubricating oil fraction having a viscosity of approximately 100 well has been completed although in some cases the material may be added to the drilling fluid during the drilling operation through the oilproducing sands. When the treatment is perwhich may pass down through the casing upon circulation of the said drilling mud in a manner similar to that employed in the conventional method of cementing wells. It may be desirable to impress additional gas or oil fluid pressure upon the liquid in the well to force the wash oil into the producing formation to be treated; The wash oil having been circulated to the producing formation, the pressure on the fluid contents of the well containing the wash oil may then be varied to cause the oil to alternately penetrate the formation and to return from the formation to the well bore thereby more effectively sombbing the sands surrounding the well bore hole and thereby at the same time carrying the dissolvedwater with the returning-wash oil to the said well bore hole from which it maysubsequently be removed. The balance of. the soluble 'wash oil remaining in the treated formation surrounding the bore hole together with its content oi.- dissolved water from the said formation is subsequently removed by the flow ofthe oil upon well, depending primarily on the diameter of the bore hole at 'the bottom of the well and on the thickness of. penetration of. the oil-producing sands. In general, however, a sumcient amount offthe wash liquid is introduced into the well to 1 force the liquid approximately four or flvefeet into the surrounding formation by the hydrostatic head of the 'combinedfluid in the bore hole. As

: stated hereinabove, a desirable method of effect? l 'ing the penetration of the wash oil into the pro- .ducing formation the required distance, is to introduce the required amount of the wash material into the'well and then place it under a superim- .posed pressure fora-sufficient time to cause'then material to penetrate into the formation and dis- 1 sec. S. U. at 100 F 85.0

100.0 Aersol (an ester of a sulfonated vbicar-- boxylic acid produced by the method disclosed in U. S. Patent No. 2,028,091) 1.0 A light naphthenic lubricating oil fraction, such as kerosene or distillates having a viscosity of approximately 45 sec.

U. at 100 F 99.0

Per cent Sulfonated oleic acid or sulfonated castor oil 20.0 Oleic acid 5.0 Alight naphthenic mineral oilfraction having a viscosity of approximately 45 sec. S. U. at 100 F 75.0

- Pounds Diglycol laurate ..,10 Ethyl alcohol 2 Naphthenic petroleum fraction having a viscosityof approximately 45 sec. S. U. at

Other materials in themselveshave been found suitable for treating the productive sands are sulfonated-fatty oils and acids and water soluble salts thereof, sulfonated mineral oil and water soluble salts thereof.- Examples of sulfonated fatty oils are sulfonated castor: and sulfonated olive oil. An example of a sulfonated mineral oil is that produced as a sulfonated byproduct of white oil manufacture, resulting from a heavy sulfuric acid treatment of a paraffin petroleum fraction which may h ve a viscosity ranging from approximately 50 sec. to 400 sec. Saybolt Universalat 100? F. V

' In practice, the, treatment of penetrated oil or gas productive sands with the soluble wash oil is preferablymade after the drilling of the solve the water contained in it. v The necessary 1 pressure to force thematerial into the formation maybe supplied by forcing a gas, such as, air or well until a suflicient the pressure may be released to atmospheric and the liquids in the well pumped or bailed out If desired, the application of the pressure onthe formationin this manner may be carried out intermittently, that is, the material introduced into the well may be maintained under pressure for a shorter period of time, say for one hour; and then the pressure released fora corresponding period of time to allow the dissolved material or emulsified water to flow back intothe well. The

pressure is then reapplied to the formation for another period of time and then again'released l and so on until the proper treainnentof the Producing formaflonhas been accomplished.

In some cases it may be necessary to repeat the above operations one or more times using fresh liquid for each operation in order to obtain the desired treatment because the liquid employed in any one operation may be contaminated with a sufficient amount of connate water or other dissolved substances before it has been able to penetrate a sufiicient distance in the oil-producing sands to accomplish the desired reduction and effective permeability thereof.

While the application of our invention is particularly suited to low producing wells in low pressure formations which have been in operation for a considerable period of time, the invention is equally well adapted to the treatment of new wells. In the treatment of new wells, however, which are initially large producers of oil or gas, it may be preferable to first bring the well into production and to allow the well to continue to produce until the oil production rate is materially 20 reduced before the treatment to remove the connate and other water in the formation is made.

The above description of our invention is not to be taken as limiting since many variations may be made by those skilled in the art within the scope of the following claims:

We claim:

1. A method of increasing the production of an oil or gas well comprising introducing a mixture of an alkali metal naphthenate and a naphthenic mineral oil fraction into the well, forcing said mixture into the interstices of the formation to contact water adsorbed therein, subsequently withdrawing said mixture together with said water from the formation and subsequently producing the Well.

2. A method according to claim 1 in which the naphthenic mineral oil fraction is a lubricating oil having a viscosity of approximately 100 seconds S'aybolt Universal at 100. F.

PHILIP H. JONES. MARC-EILUS T. FLAXMAN. 

